1. Field of the Invention
The present invention relates to a mobile communication terminal and to a mobile communication terminal capable of preventing loss, theft or unauthorized use of the mobile communication terminal in particular.
2. Description of the Related Art
With the diffusion of the mobile phone, the loss or theft thereof has become a major problem. When a mobile phone has been lost there is a risk that a third party may use the mobile phone without permission or that information contained therein may leak out.
A large number of mobile communication terminals provided with a protection function against unauthorized use has already been proposed. Patent Laid-Open 2004-69883, Patent Laid-Open 2002-218542 and Patent Laid-Open 2002-183866 disclose a warning device that separates from the phone. The warning device receives a weak radio signal transmitted by the mobile phone. When the receiving signal level has dropped and reception is disabled, the warning device generates the previously set warning. With these technologies, however, the warning devices only gives a warning and is, consequently, not capable of preventing unauthorized use after loss or theft. Patent Laid-Open 2002-300651 discloses a protection system for preventing the unauthorized use of a portable information terminal by using a wristwatch. The wristwatch and the portable information terminal mutually conduct short-distance wireless communication. When the portable information terminal cannot receive the transmission packet that is regularly sent from the wristwatch, the portable information terminal will not operate without entering the previously registered password or fingerprint. In this system, it is necessary to enter the previous settings for user verification and the use needs to carry both the special-purpose wristwatch and the portable information terminal.